The present invention relates to copper-base spinodal alloys and, in particular, copper-base spinodal alloys also containing nickel and tin.
Ternary copper-nickel-tin spinodal alloys are known in the metallurgical arts. As one example, U.S. Pat. No. 4,373,970 discloses spinodal alloys prepared by powder metallurgy containing from about 5 to 35 weight percent nickel, from about 7 to 13 weight percent tin, and the balance copper. The alloys disclosed by this prior art patent exhibit in the age hardened spinodally decomposed state a highly desirable combination of mechanical and electrical properties, i.e. good strength and good electrical conductivity, and thus have valuable utility as a material of construction for articles of manufacture such as electrical connectors and relay elements. One particular ternary spinodal alloy composition falling within the scope of the disclosure of U.S. Pat. No. 4,373,970 contains about 15 weight percent nickel and about 8 weight percent tin and is sold commercially under the trade name of Pfinodal (Pfizer Inc.; New York, N.Y.). This alloy composition combines a sufficient strength for many commercial applications with a good ductility and an excellent electrical conductivity.
A quaternary spinodal alloy consisting essentially of from about 5 to about 30 percent by weight nickel, from about 4 to about 13 percent by weight tin, from about 3.5 to about 7 percent by weight cobalt and the balance copper, with the sum of the nickel and cobalt contents being no more than 35 percent by weight of the alloy, is disclosed in my U.S. Pat. No. 4,525,325. This alloy exhibits improved ductility, formability and electrical conductivity in the age hardened spinodally decomposed state without substantial diminishment of strength properties in that state, all as compared to a ternary Cu-Ni-Sn alloy in which the nickel content equals the sum of the nickel and cobalt contents in the quarternary alloy. Said U.S. Pat. No. 4,525,325 is incorporated herein by reference in its entirety.
Other copper base spinodal alloys containing nickel and tin are disclosed in U.S. Pat. Nos. 3,937,638; 4,012,240; 4,090,890; 4,130,421; 4,142,918; 4,260,432 and 4,406,712, and U.S. Pat. Re. No. 31,180 (a reissue of U.S. Pat. No. 4,052,204). Of particular interest is U.S. Pat. No. 4,130,421 which discloses the presence of up to 0.2 percent cobalt in a quaternary spinodal copper-nickel-tin-(Se, Te, Pb or MnS) alloy. According to this prior art patent, however, cobalt is not a desired additive and the 0.2 percent level is said to be a preferred upper limit placed on cobalt as an impurity.
Quaternary copper-nickel-tin-cobalt alloys are disclosed in U.S. Pat. No. 3,940,290 and 3,953,249. These alloys contain only 1.5% to 3.3% tin and thus do not appear to be spinodal alloys. Furthermore, these prior art patents teach that the cobalt level in the alloy should not exceed 3% in order to minimize impairment of ductility and hot workability.
Japanese Published patent application No. 5942/81 (published Jan. 22, 1981) discloses a series of cast copper-base quaternary spinodal alloys containing 9 wt. % nickel and 6 wt. % tin including, inter alia, alloys containing 0.5, 0.8 and 2.0 wt. % cobalt, respectively, as the quaternary element.